I'm researching Sgt Stan Holt who was lost returning from a mission on 29/30 April 1941. I have downloaded the squadron's operations record book for April from the national archive but there are a couple of abbreviations I've not been able work out. I've searched every combination online but none of the online glossaries seem to contain them.

The record for the flight says:

Aircraft failed to return.N.A.P. was sent at 00.50hrs and the last thing heard of the aircraft was S.O.S. at 03:14hrs. previous to which the aircraft was homing on Waterbeach D/F.

I'd like to clarify what N.A.P. stands for and D/F

Any help would be gratefully recieved as I think I've exhausted all options with google searches.

All the best
Andy Holt (Stan's nephew)